This marks the first use of International Rescue's personal defense weapon.
Tin-Tin can be seen smoking for the first and only time in the series
When Scott asks Wilson and Lindsey to radio International Rescue to inform them that he is ok, he mentions that any radio frequency will do for the call. This is the first mention of Thunderbird 5's ability to pick up radio calls on any frequency.
The long shots of Scott hanging out of the window/hatch of Thunderbird 1 as Wilson and Lindsey find him, shows white lettering around the window (presumably "TB1") but the close ups show no white around the window at all.
As Thunderbird 1 crashes in the desert, Scott is thrown forwards and bangs his chin on TB1's flight controls. However he would later be shown with his forehead on the controls.
Between arriving on board Thunderbird 3 and climbing into the elevator to travel up to the control room, Alan completely changes his clothes from a purple suit to green checked shirt and beige trousers. (It uses the same footage from 'Sun Probe'). Similarly, Scott returns from Thunderbird 3 wearing different clothes from those that he left in, swapping a yellow suit and orange shirt for his usual blue roll-neck and checked jacket.
When Tin-Tin responds to news of Scott's disappearance, a floor puppeteer's hand (with dirty fingernails!) can be seen in the bottom of the screen lifting Tin-Tin from her seat.
It makes no sense for the logo in the Zombites' control room to be a reversed image of the logo on their helmets.
When Scott returns from picking up John, where is John, as he does not appear with Scott when returning to the Tracy Island lounge?
Lindsay: Maybe there are other people here
Wilson: Hello! Anyone there? Hello!
Lindsay: Not a sound. Only that splashing water
Wilson: There it is!
Lindsay: The eternal fountain
Lindsay: We're rich, Wilson. The richest men alive!
Wilson: Yeah. Yeah. We could buy the world. Say, we've forgotten something. We're trapped in here. We couldn't open that entrance door.
Lindsay: We can't be. We're too rich to be trapped.
This episode is also known as "The Uninvited: Alien Attack."
Although credited on the end titles, Sylvia Anderson does not take part in this episode.
Lady Penelope, Parker and Kyrano don't appear in this episode.
Originally scripted as a 25-minute episode, some of the elements used to bring it up to 50 minutes included Thunderbird 1 being shot down in the Sahara desert. This was the first 50-minute episode to be recorded.